In recent years, microRNAs (miRs) have emerged as an important novel class of regulatory RNA, which have a profound impact on a wide array of biological processes.
These small (typically 18-24 nucleotides long) non-coding RNA molecules can modulate protein expression patterns by promoting RNA degradation, inhibiting mRNA translation, and also affecting gene transcription. miRs play pivotal roles in diverse processes such as development and differentiation, control of cell proliferation, stress response and metabolism. The expression of many miRs was found to be altered in numerous types of human cancer, and in some cases strong evidence has been put forward in support of the conjecture that such alterations may play a causative role in tumor progression. There are currently about 700 known human miRs, and their number probably exceeds 800.
Classification of cancer has typically relied on the grouping of tumors based on histology, cytogenetics, immunohistochemistry, and known biological behavior. The pathologic diagnosis used to classify the tumor taken together with the stage of the cancer is then used to predict prognosis and direct therapy. However, current methods of cancer classification and staging are not completely reliable.
Lung cancer is one of the most common cancers and has become a predominant cause of cancer-related death throughout the world. Scientists strive to explore biomarkers and their possible role in the diagnosis, treatment and prognosis of specific lung cancers.
Making the correct diagnosis and specifically the distinction between lung squamous carcinoma and other Non Small Cell Lung Carcinoma (NSCLC) such as but not limited to lung adenocarcinoma, has practical importance for choice of therapy. Severe or fatal hemorrhage is a black box warning for lung squamous carcinoma patients undergoing bevacizumab (Avastin) therapy. To-date there is no objective standardized test for differentiating squamous from non squamous NSCLC.
The search for biomarkers for the early detection and accurate diagnosis of various NSCLC has met with little success. Much emphasis has been placed on the discovery and characterization of a unique tumor marker. However, no marker has been identified that has adequate sensitivity or specificity to be clinically useful, although a combination of multiple markers has been shown to increase diagnostic accuracy.
There is an unmet need for a reliable method for distinguishing between lung squamous cell carcinoma and other NSCLC.